A point-to-point system that uses parabolic antennas is used as a mobile backhaul radio system. In order to provide good-quality communication, line of sight between antennas is required. In other words, in order to ensure line of sight, antennas need to be installed in elevated locations. Modern mobile station cells have been reduced to small cells such as picocells and femtocells. Consequently, base stations in urban regions need to be installed at lower locations. This poses a problem that line-of-sight environments cannot be ensured and that it makes it difficult to provide radio communication in point-to-point systems.
Patent Literature 1 (PTL1) proposes that a passive repeater made up of two antennas coupled back to back is provided at a midpoint between a transmitting antenna and a receiving antenna to prevent disconnections due to fading.
The use of the repeater as described in Patent Literature 1 (PTL1) allows good-quality communication even when the angle of incidence is large. However, the passive repeater, which is made up of two antennas coupled back to back, has the problem of high cost because it requires two antennas.
A related technique that addresses the problem is a reflector relay method described in Non Patent Literature 1 (NPL1) which is a method for relaying microwaves between two points that are not on a direct line-of-sight path. Patent Literature 2 (PTL2) proposes that a reflector having two reflective surfaces that face each other at an angle of approximately 90 degrees is used as a relay station, one terminal station transmits a signal toward the reflector and the signal reflected by the two reflective surfaces is received at another terminal station. Patent Literature 3 (PTL3) proposes that a radio wave from a wireless base station is reflected by a curved reflector plate to eliminate blind regions in a mobile communication system. Patent Literature 4 (PTL4) proposes an RFID (radio frequency identification) communication system in which a reflector plate is attached to a motor shaft at an inclination angle to the motor shaft and an electromagnetic wave from an antenna is reflected toward an RFID tag by the reflector plate which rotates about the motor shaft.
Point-to-point systems can be provided in non-line-of-sight environments by using the repeater systems described in Patent Literatures 2 to 4 (PTL2 to PTL4) and Non Patent Literature 1 (NPL1).